Oil is commonly collected from below surface reservoirs using a tubing string. Typically the tubing string is constructed in threaded sections and includes an inline pump. The pump considered is a screw-type pump including a rotary drive, a stator and a screw type rotor rotatable therein. The pumps are commonly of right-hand rotation and under certain conditions can transmit large forces to the tubing string. This tends to rotate the tubing string and release the threaded sections which is undesirable.
This problem has been addressed by J. L. Weber in Canadian Patent No. 1,274,470, which discloses a "No-Turn.TM. Tool" for preventing such rotation of a tubing string. The device comprises an outer tubular housing which rotates about an inner mandrel. The housing holds four retractable slips which are extended for anchoring the device to the stationary well casing. Right-hand rotation of the inner mandrel relative to the housing engages cams which extend the slips into the well casing. Rotation in the opposite direction disengages the cams and the slips are pushed away from the well casing by springs. The device is relatively complex, using both springs and cams, resulting in significant manufacturing costs.
Also addressing the problem of rotation of a tubing string, U.S. Pat. No. 5,275,239 to M. Obrejanu discloses a device for anchoring a tubing string within a stationary well casing against right-hand rotation. The device has four anchoring mechanisms spaced circumferentially about a main housing. Each anchoring mechanism includes a recess and an anchoring member free-floating within the recess. A spring urges the anchoring member outward to engage the well casing. Right-hand rotation of the device will rotate the anchoring members into a locking position. The device is also complex, requiring a spring for each anchoring member. The anchoring members are free-floating and can jam, making the device less reliable.